Tess Holliday is feeling stronger in both her body and her mind after a workout with her new trainer, Massy Arias.

The model, 33, shared a video from her session with the fitness influencer, and admitted to dealing with some body insecurities after watching the footage.

“@massy.arias kicked my butt today! Not gonna lie to y’all — seeing my body from some of these angles made me feel badly at first, and then had to remind myself who I am. I’m fat and fooooooine,” Holliday captioned the Instagram post.

Arias ran Holliday through several exercises — including squat holds, arm presses and opposite leg raises — using two gallon-size water bottles as weights.

The trainer said she focused the session on core work to build up Holliday’s ab muscles.

“Emphasis is on strengthening her core and complex movements that require different muscles so we burn burn burn,” Arias wrote in her own Instagram post. “Pay attention to the core moves as they are staple when trying to build a strong core (specially my mamas out there). The goal to a successful fit journey is to make sustainable goals. Start small, and build from it. Keep growing by learning your body. Make it fun! This is only the beginning, and I’m so proud of this woman!”

Holliday announced in July that she and Arias were teaming up to spread a message of body positivity to their combined 4.5 million Instagram followers.

“I’m excited to start my new journey with @massy.arias,” Holliday wrote. “We’ve been following each other for quite a while on IG and I finally reached out to her about being my new trainer … Our view points align that every BODY is valid, that size isn’t an indicator of health and we are both feminists raising tiny lil feminists to rule the world!”